Read the Incose 2008 OMGSysML tutorial that is published in PDF format.
Not only does this explain SysML in the simplest terms, it is probably one of
The best sources to learn SysML thoroughly.
You can obtain a copy of this document at this website ( if it’s still hosted when you visit the site of course)
http://www.sysmlforum.com/training.htm
Enjoy.